In the last few years several catalysts have been reported for olefin polymerization. The polymerization catalysts reported by Brookhart perform in the presence of methylaluminoxanes and Lewis acids (1). Several patents have been filed based on these catalysts, (See WO09623010 and references therein). These catalyst systems are thermally unstable and the activity of the methylaluminoxane activated catalysts decays rapidly at 60° C. (2), and the borane activated catalysts are decomposed at room temperature (3). Another type of catalyst is those reported by Younkin et al., (4). These are neutral species that do not require an activator. However, they are prone to an induction period and lower activity compared with the cationic Brookhart systems. PCT application WO01/92348 describes the polymerization of ethylene and the co-polymerization of ethylene using zwitterionic nickel complexes that require the presence of a Lewis acid. Lewis Acids are deactivated by functionalities and they promote unwanted secondary reactions, e.g., chain transfers that are detrimental to the polymer chain growth.
Despite the foregoing, interest in metal-mediated polymerization of olefins remains unabated in academic and industrial laboratories (5, 6, 7, 8, 9, 10, 11, 12, 13, 14). Furthermore, despite the foregoing, there is a need in the field for single component catalytic systems that offer better control over polymerization reactions and lower overall costs.